imo calling and 3betting preflop are both fine, but I would incline to 3bet as MP1 could call us with worse hands (stacksize).

As played we could bet more on flop for value from flushdraws, worse Ax.

Turn is a check/fold for me. As we are 3way, the probability that someone holds flush rises. MP1 didn't cbet but check/called instead - looks like a draw or weak Ax to me. You can get value from Ax on river if he checks again.